The invention relates to a compressor in an exhaust gas turbocharger for an internal combustion engine wherein the compressor has a compressor wheel which is rotatably supported in a compressor inlet duct together with an auxiliary rotor arranged adjacent the compressor wheel.
DE 100 61 847 A1 discloses an exhaust gas turbocharger having an exhaust gas turbine in the exhaust system and having a compressor in the intake tract of the internal combustion engine. Mounted upstream of the compressor wheel in the inlet duct of the compressor is a separate auxiliary rotor wheel, which is situated upstream of the compressor wheel in the flow direction of the combustion air which is supplied via the inlet duct. The auxiliary rotor wheel has the function of favorably influencing the operating behavior of the compressor by a displacement of the surge limit and the choke limit of the compressor for the benefit of an expanded operating characteristics diagram. The auxiliary rotor wheel rotates independently of the compressor wheel and is driven by an electric motor.
A coupling between a blocking element for adjusting the free flow cross section in the compressor inlet duct and the compressor wheel is described in DE 103 10 650 A1. The blocking element is the support of a stator of an electric motor, and an associated rotor is fixedly connected to the compressor wheel of the compressor. The blocking element is axially adjustable in the compressor inlet duct, with the stator and the rotor assuming a functional position, in which additional drive energy is introduced into the compressor wheel, when the blocking element is in a position close to the compressor wheel. It is possible in this way, in particular at low loads and speeds of the internal combustion engine, at which only a low exhaust gas pressure is available for driving the turbine of the exhaust gas turbocharger, to keep the charger speed at an increased level. A prerequisite, however, is the introduction of electrical drive energy.
DE 199 55 508 C1 discloses an exhaust gas turbocharger for an internal combustion engine whose compressor has an additional flow duct parallel to the compressor inlet duct, with the additional flow duct opening out radially towards the compressor wheel blades. This makes it possible for air to be introduced via the additional duct to the radial outer side of the compressor wheel blades, so that a rotational drive impetus can be imparted to the compressor wheel blades in operating states of the internal combustion engine in which a low pressure vacuum prevails at the cylinder inlets. The prevailing pressure drop across the compressor in the operating states is therefore utilized to drive the compressor wheel, the compressor being driven in the so-called cold air turbine mode, making it possible for the charger speed of the exhaust gas turbocharger to remain at an increased level in all operating ranges.
Based on the prior art, it is the object of the present invention to keep the charger speed in the exhaust gas turbocharger at a high level in all operating ranges of the internal combustion engine using simple design measures. This should expediently take place without the introduction of additional drive energy.